The present invention relates to a semiconductor device, and more specifically, to a semiconductor device including a buried gate and a fabricating method of the same.
A typical semiconductor memory device is a dynamic random access memory (DRAM). A DRAM device includes a plurality of unit cells each of which includes a capacitor and a transistor. The capacitor is used for temporarily storing data and the transistor is used for transferring the data between a bit line and the capacitor in response to a control signal (word line). The transistor has three regions, i.e., a gate, a source and a drain. According to a control signal inputted to the gate, an electric charge moves between the source and the drain. The movement of the electric charge between the source and the drain is performed through a channel region. The properties of the semiconductor are used for forming this channel.
In the case of fabricating a conventional transistor on a semiconductor substrate, the gate is formed on the semiconductor substrate and the source and the drain are formed by doping both sides of the gate with impurities. In this case, under the gate, between the source and the drain, there is the channel region of the transistor. Such a transistor having a horizontal channel region occupies a certain area of the semiconductor substrate. In case of a complex semiconductor memory device, it is difficult to reduce a whole size due to a plurality of transistors included in the semiconductor memory device.
If the size of the semiconductor memory device is reduced, the number of semiconductor memory devices produced per wafer can be increased and thus productivity can be improved. For reducing the size of the semiconductor memory device, various methods have been proposed. One of these is to use a recess gate instead of a conventional planar gate having the horizontal channel region. That is, a recess is formed in the semiconductor substrate and the gate is formed in the recess so that the channel region is formed along a multi-plane surface of the recess. For more improvement from the recess gate structure, a buried gate formed by burying an entire gate within the recess is researched.